In recent years, piezoelectric vibrators using a piezoelectric vibrating reed formed of a piezoelectric material such as crystals or the like have been used in mobile phones or personal digital assistants, as time sources or timing sources such as control signals, or reference signal sources and the like. As the piezoelectric vibrating reed, a tuning fork type piezoelectric vibrating reed including a pair of vibration arm portions has been adopted.
As this type of piezoelectric vibrator, a Surface Mount Device (SMD) type piezoelectric vibrator is known.
FIG. 16 is a plane view of a state in which a lid substrate of a surface mount type piezoelectric vibrator according to the related art is removed, and FIG. 17 is a cross-sectional view taken from line C-C of FIG. 16. As shown in FIG. 17, as an SMD type piezoelectric vibrator 200, a piezoelectric vibrator, in which a package 209 is formed by a base substrate 201 and a lid substrate 202 and a piezoelectric vibrating reed 203 is received in a cavity C formed in an inner portion of the package 209, is suggested. The base substrate 201 and the lid substrate 202 are bonded to each other by anode bonding by arranging a bonding film 207 therebetween.
Generally, it is desired that a piezoelectric vibrator suppresses the equivalent resistance value (effective resistance value, Re) to a lower level. Since a piezoelectric vibrator having a low equivalent resistance value can vibrate the piezoelectric vibrating reed using less electric power, it is a more energy efficient piezoelectric vibrator.
As a general method of suppressing the equivalent resistance value, a method of making the inside of the sealed cavity C of the piezoelectric vibrating reed 203 closer to a vacuum shown in FIG. 16 is known, thereby lowering a series resonance resistance value (R1) that has a proportional relationship with the equivalent resistance value. As a method of making the inner portion of the cavity C closer to a vacuum, there is a known method (known as gettering) of sealing a getter material 220 formed of aluminum or the like in the cavity C and irradiating laser from the outside to activate the getter material 220 (see Patent Document 1). According to this method, since oxygen generated during anode bonding can be absorbed by the getter material 220 entering the activation state, the inner portion of the cavity C can be made closer to a vacuum.
[Patent Citation 1] JP-A-2003-142976